Bi-radial patient interface

ABSTRACT

To improve the precision of ophthalmic surgical procedures by reducing corneal wrinkling, a patient interface for an ophthalmic system can include an attachment portion, configured to attach the patient interface to a distal end of the ophthalmic system; a contact portion, configured to dock the patient interface to an eye; and a contact element, coupled to the contact portion, configured to contact a surface of a cornea of the eye as part of the docking of the patient interface to the eye, and having a central portion with a central radius of curvature Rc and a peripheral portion with a peripheral radius of curvature Rp, wherein Rc is smaller than Rp.

BACKGROUND Field of Invention

This patent document relates to patient interfaces that attach anophthalmic system to an eye for anterior segment eye procedures. Moreparticularly, this patent document relates to bi-radial patientinterfaces that reduce a deformation of a cornea of the procedure eye.

Description of Related Art

This patent document describes examples and embodiments of techniquesand devices for securing an ophthalmic system to an eye. The ophthalmicsystem may be an ophthalmic surgical laser system to perform an anteriorsegment eye procedure, such as a cataract procedure. These devices areoften referred to as patient interfaces. A patient interface serves toconnect and to couple the ophthalmic system and the eye of the patient,thus their performance is an important controlling factor of theprecision and success of the ophthalmic procedures. Therefore,improvements in patient interfaces can lead to improvements in theprecision and reliability of ophthalmic procedures.

SUMMARY

Briefly and generally, embodiments of the present invention are capableof reducing corneal wrinkling, one of the factors that hinder theprecision of ophthalmic surgical procedures. The causes of cornealwrinkling include a pressure exerted by the weight of the patientinterface and an objective of an optical system on the eye; acompressive force, generated by a negative pressure of a suction systemto immobilize the patient interface relative to the eye; a mismatchbetween the radius of curvature of the patient interface and that of thecornea of the eye; the complex shape of the surface of the cornea; andthe variation of the corneal radius of curvature from patient topatient.

To improve the precision of ophthalmic surgical procedures by reducingcorneal wrinkling, a patient interface for an ophthalmic systemaccording to embodiments of the present invention can include anattachment portion, configured to attach the patient interface to adistal end of the ophthalmic system; a contact portion, configured todock the patient interface to an eye; and a contact element, coupled tothe contact portion, configured to contact a surface of a cornea of theeye as part of the docking of the patient interface to the eye, andhaving a central portion with a central radius of curvature Rc and aperipheral portion with a peripheral radius of curvature Rp, wherein Rcis smaller than

Rp.

Embodiments of a method of docking a patient interface of an ophthalmicsurgical laser system to an eye can include: determiningR(central-cornea), a radius of curvature of a central portion of acornea of the eye, and R(peripheral-cornea-sclera), a radius ofcurvature characteristic of a peripheral portion of the cornea and asclera of the eye; selecting a contact element with a central portionhaving a central radius of curvature Rc and a peripheral portion havinga peripheral radius of curvature Rp that is greater than Rc, wherein Rcis less than R(central-cornea)+1 mm, and Rp is less thanR(peripheral-cornea-sclera)+1 mm; and docking the patient interface ofthe ophthalmic surgical laser system with the selected contact elementto the eye.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an ophthalmic surgical laser system.

FIGS. 2A-B illustrate the wrinkling of the cornea during docking withsome patient interfaces.

FIG. 3 illustrates a one-piece patient interface with a bi-radialcontact element.

FIG. 4 illustrates a two-piece patient interface with a bi-radialcontact element.

FIG. 5 illustrates a method of using a patient interface with abi-radial contact element.

DETAILED DESCRIPTION

Some laser eye surgical procedures, such as corneal refractivecorrections, and laser-assisted lens photodisruptions and capsulotomies,may benefit from immobilizing the procedure eye relative to theophthalmic surgical laser system during the procedure. Some ophthalmicsurgical laser systems make use of a so-called patient interface tocarry out this task. A proximal portion of the patient interface can beattached to a distal end of the surgical laser system, such as to itsobjective. A distal portion of the patient interface can include acontact lens. The patient interface can be docked to the eye by pressingit to the eye and then applying suction to a space between the patientinterface and the eye. When the patient interface is docked to the eye,the contact lens is pressed against the cornea of the eye. The pressureand suction of the patient interface holds the eye steady relative tothe surgical laser system, and the contact lens provides awell-controlled optical coupling to the eye. Both these attributesenable a high precision directing and focusing of the laser beam topredetermined target locations within the eye.

Some patient interfaces use flat contact lenses, also called applanationplates. Others include single-radius of curvature curved contact lenses.To prevent the slipping and rolling of the eye, caused by theslipperiness of the tear film covering the eye, these contact lenses arepressed against the cornea of the eye by mechanical forces and byapplying suction by a vacuum system to a surrounding suction ring.

While using single-radius of curvature contact lenses has the benefit ofproviding a well-defined and simple optical element for optimizing thebeam properties of the laser beam of the ophthalmic system, and possiblya reference plane to direct the surgical laser with precision, their usecan also lead to problems that include the following.

(1) Bubbles are often trapped under the contact lens during docking. Toavoid this bubble formation, the radius of curvature of thesingle-radius-of-curvature contact lenses is typically chosen to belarger than that of the cornea. A typical corneal radius of curvature inthe central portion (in the central-cornea) is in the range of 7.2-8.0mm, quite often close to 7.6 mm. Accordingly, the radius of curvature ofsingle-radius-of-curvature contact lenses is often chosen to bedistinctly larger than these values, often in the 10-15 mm range. The10-15 mm range for the radius of curvature can be useful to optimize thewavefront of the laser beam 112 and to minimize its aberrations.

However, such a large mismatch of the radius of curvature of the contactlens and that of the cornea can lead to the problem that upon docking tothe eye the contact lens flattens and thus wrinkles the surface of thecornea. These wrinkles can distort the laser beam, leading to increasedscattering of the beam, and reducing its power below a photodisruptionthreshold, possibly making the important capsulotomy cuts of thecataract surgery incomplete. If, in response, the power of the laserbeam is increased to overcome the increased scattering by the wrinkles,then the higher power can damage the photosensitive tissues of the eye,such as the retina, especially when scanning the beam through regionswhere the cornea is not wrinkled. Wrinkling can also reduce theprecision of the targeting of the laser beam.

(2) Using single-radius-of-curvature contact lenses can wrinkle thecornea for the additional reason that the frontal surface of the eye ismore complex than that of the single radius contact lens. It includes acentral-cornea with a radius of curvature R(central-cornea) in the 7-8mm range, with a typical radius of curvature of about 7.6 mm.Surrounding the central-cornea is a peripheral-cornea, whose radius ofcurvature R(peripheral-cornea) can gradually increase from 8 mm up to 11mm. Surrounding the peripheral-cornea is the sclera, whose radius ofcurvature R(sclera) is markedly different from the central-cornea: it isin the 9-14 mm range, often in the 9.5-12 mm range. Asingle-radius-of-curvature contact lens and a frontal eye surface thathas two or even three distinct radii are mismatched to a degree thatupon docking the patient interface on the eye, the mismatch can cause asubstantial wrinkling of the cornea.

(3) The mismatched radius of curvature of the contact lens and itssingle-radius-of-curvature structure can not only wrinkle the cornea butcan also cause internal deformations since the support system of theinternal lens of the eye is very soft. Therefore, the docking of asingle-radius of curvature, mismatched contact lens typically shifts andtilts the lens of the eye relative to the optical axis of the eye. Thisdisplacement and tilt may make the cuts of a typical cataract surgery,including the critical capsulotomy cut on the capsular bag and thecataract surgical cut-pattern inside the lens, off-center and distorted,leading to a deterioration of the optical outcome of the cataractprocedure.

For all these reasons, developing new types of contact lenses that donot have a single-radius-of-curvature structure and a mismatched radiusof curvature can improve the performance of ophthalmic surgical lasersystems. Embodiments of the present invention offer solutions for thehere-outlined problems and challenges.

FIG. 1 illustrates an imaging-guided ophthalmic surgical laser system100. The surgical laser system 100 can include an ophthalmic laser 110that can generate a surgical laser beam 112. The surgical laser beam 112can be a pulsed beam with pulse length in the 1-1,000 femtosecond range.The laser beam 112 can have a power sufficient to cause photodisruptionin an ophthalmic target tissue. The laser beam 112 can be coupled intoan optic 120 via a beam splitter BS1. Optic 120 can focus and direct thelaser beam 112 to a target point in a target region of a procedure eye20 of a patient 10 through an objective 130. With the help of scanningmirrors and actuators, optic 120 can also scan the laser beam 112through a sequence of target points to cut the eye tissue along asurgical cut pattern.

The procedure eye 20 can be immobilized relative to the surgical lasersystem 100 with a patient interface 200 to prevent involuntary movementsof the eye 20 and thus to enhance the precision and reliability of thesurgical procedure. Patient interface (PI) 200, attached to theobjective 130 at a proximal end, can be docked to the eye 20 with avacuum suction system. To dock the PI 200 to the eye 20, the objective130 can be aligned with the eye 20 by a gantry 132.

Surgical procedures can be aided by including various imaging systemsinto the surgical laser system 100. A video imaging system 140, such asa video-microscope, can be included in the surgical laser system 100that images the eye 20 and displays it on a video-image display 144. Insome embodiments, the video-imaging system 140 can also include avideo-image processor 146 to process the video image. Such video-imagingsystems 140 can provide a frontal view of the eye 20, but typicallyprovide limited information of the depth, or z-directional structure ofthe eye 20.

In order to provide depth, or z-directional, imaging, the surgical lasersystem 100 can include a depth-imaging system 150. The depth-imagingsystem 150 can include an optical coherence tomography (OCT) imagingsystem, a Scheimpflug imaging system, a slit-lamp system, orequivalents. The depth-imaging system 150 can emit an imaging beam 152that is coupled into the optic 120 by a beam splitter BS2 and directedto the target by the optic 120. The imaging beam 152 can be reflectedfrom the eye 20 and returned to the depth-imaging system 150 where itgets analyzed and displayed on a depth-image display 154. In someembodiments, a depth-image processor 156 can be included to process thedepth-image, such as to recognize edges and to reduce noise. In somesurgical laser systems 100 the video-imaging system 140 and thedepth-imaging system 150 can be coupled.

Finally, the surgical laser system 100 can also include a dockingguidance system 160 to guide the docking of the patient interface 200.The docking guidance system 160 can include a gantry controller 162 thatcan move the gantry 132 to align the objective 130 with the eye 20. Insome embodiments, a fixation light source 164 can be also included toproject a fixation light beam 166 into a control eye 20 c or into theeye 20 through the objective 130. The fixation light beam 166 can beadjusted to direct the patient to rotate his/her eyes to further improvethe alignment with the objective 130. Some of the operations of theguidance system 160 can be computer-controlled and can be based on theoutput of the video-image processor 146 and the depth-image processor156.

FIGS. 2A-B illustrate the docking of the patient interface 200 on theeye 20 in more detail. The patient interface (PI) 200 can include anattachment portion 210 to attach the PI 200 to the objective 130, acontact portion 220 that is docked to the eye 20, and a distal lens 230that optically couples the surgical laser beam 112 and the imaging beamsinto a cornea 21 of the eye 20. The contact portion 220 can include asuction skirt or suction ring 222 that has a suction port 224. Thissuction port 224 can be coupled to a vacuum or suction system to applyvacuum or negative pressure that expels air from a contact space 226,thus pressing the distal lens 230 onto the cornea 21.

In an ideal operation, the laser beam 112 propagates through the optic120, objective 130 and distal lens 230 to arrive to the target of theophthalmic surgical procedure, such as a lens 22 of the eye as a focusedbeam 112 f, and to form precise surgical cuts. However, FIG. 2Billustrates that under some circumstances the pressure of docking canwrinkle the cornea 21. These wrinkles can scatter the laser beam 112into a scattered beam 112 s that has lower power at the target and thusmay be unable to perform the surgical cuts. Also, the scatter laser beam112 s may be deflected or misdirected by the wrinkles. The lowered beampower and misdirection can have various negative consequences, asdiscussed earlier.

FIG. 3 illustrates a patient interface (PI) 300 according to embodimentsof the invention that is configured to reduce the corneal wrinklingrelated to docking. The patient interface 300 can include an attachmentportion 310, configured to attach the patient interface 300 to a distalend of the ophthalmic surgical laser system 100, in particular to itsobjective 130. The attachment portion 310 can include a bayonet lock, asnap-on lock, or locking flanges, for example. It can be made of plasticor another flexible material.

The PI 300 can also include a contact portion 320, configured to dockthe patient interface 300 to the eye 20. The contact portion 320 caninclude a suction skirt or suction ring 322 that has a suction port 324.The suction port can be attachable to a vacuum or suction system thatcan apply negative pressure or suction to a contact space between the PI300 and the cornea of the eye. With this design, the contact portion 320can attach the PI 300 to the eye and thus immobilize the eye 20 relativeto the surgical laser system 100. The PI 300 can also include a distallens 330 that can optically couple the laser beam 112 into the cornea ina controlled manner. The distal lens 330 can be a rigid or hard lenswith well-defined optical characteristics.

In addition to these elements, the patient interface 300 can alsoinclude a contact element 340 that is coupled to the contact portion320. The contact element 340 can be configured to contact a surface ofthe cornea as part of the docking of the patient interface 300 to theeye. Embodiments of the contact element 340 can reduce the cornealwrinkling by having a structure different from existing contact lensesin that they can have two portions with different radii of curvatures: acentral portion 342 with a central radius of curvature Rc and aperipheral portion 344 with a peripheral radius of curvature Rp, whereinRc is smaller than Rp. Such designs can have various advantages.

(1) Structure Matching:

Because of the added design degree of freedom of having two radiiinstead of one, in general the bi-radial structure of the contactelement 340 can mirror and accommodate the complex frontal surface ofthe eye better than single-radius-of-curvature contact elements, thusreducing wrinkling compared to a single-radius-of-curvature contactelement.

(2) Radius Matching:

In addition to the advantage of having a bi-radial structure in general,in some embodiments in particular the radii Rc and Rp can be chosen tobe close to the central-corneal radius of curvature R(central-cornea)and the scleral radius of curvature R(sclera), thus further reducing thepreviously discussed radial mismatch, flattening and wrinkling. In someembodiments, Rc can be in the range of 6.6 mm-9.1 mm and Rp in the rangeof 8.8 mm-10.8 mm. In other embodiments, Rc can be in the range of 7.1mm-8.1 mm and Rp in the range of 9.3 mm-10.3 mm. It is recalled herethat the central corneal radius of curvature R(central-cornea) istypically in the range of 7-8 mm, often close to 7.6 mm, and the radiusof curvature of the sclera R(sclera) is typically in the range of 9-14mm, often in the range of 9.5-12 mm. Therefore, the above listed rangesof Rc and Rp can provide a close match between the patient interface 300and the central-cornea 21 and the sclera 24. Since from now on thecorneal structure will be discussed in more detail and resolution, label21 will refer only to the central-cornea and label 23 to theperipheral-cornea, as shown in FIG. 3.

It is noted here that the radii of the frontal eye surface have a broaddistribution in various patient groups. A very small percentage ofpatients have been identified with radii outside the above ranges: theyconstitute the tails of the radius distribution. Therefore, statementsabout ranges of radii here refer to a representative range of the largemajority of the patient population, and may not include the farthestoutlying few percent tail of the distribution.

Bi-radial patient interfaces whose radii approximately match the radiiof the central cornea and that of the sclera offer advantages overexisting single-radius-of-curvature, mismatched patient interfaces.Approximately matching the central radius of curvature Rc to that of thecentral cornea R(central-cornea) can efficiently reduce or eveneliminate the wrinkling of the cornea, since docking the contact element340 does not exert a flattening effect on the central cornea anymore.Also, approximately matching the peripheral radius of curvature Rp toR(sclera) can allow the efficient suction and removal of bubbles, formedduring docking, along the contact surface between the peripheral portion344 and the cornea. The removal of the bubbles can be further eased andassisted by applying lubricants to the contact surface.

Given the complex frontal surface of the eye, in some embodiments, Rpmay not be matched to the radius of curvature of the sclera R(sclera)alone, but rather can be chosen to be characteristic of both theperipheral-corneal radius of curvature R(peripheral-cornea) and scleralradius of curvature R(sclera).

In the above discussions, Rc and Rp represent radii of curvatures. Thecentral portion 342 of the contact element 340 also has a lateralcentral-diameter Dc. This lateral central-diameter Dc is different fromthe radii of curvature: in a Cartesian coordinate system with its Z axisalong the optical axis of the objective 130, the radii of curvature Rcand Rp are defined in an XZ or a YZ plane, whereas the lateralcentral-diameter Dc is defined in the XY plane. In addition, theperipheral portion 344 of the contact element can have aperipheral-diameter Dp.

To discuss the relation of the diameters Dc and Dp to the cornealdiameters, it is recalled here that a diameter of the central-cornea 21D(central-cornea) can be in the 6-9 mm range and a diameter of theperipheral-cornea D(peripheral-cornea) in the 10-12 mm range, oftenabout 11 mm. D(peripheral-cornea) is where the peripheral-cornea 23meets the sclera 24 and thus a relatively well-defined quantity. On theother hand, the radius of curvature of the cornea varies from its valueR(central-cornea) in the central-cornea 21 somewhat gradually towardsits value R(peripheral-cornea) in the peripheral-cornea 23. Therefore,the transition line between these portions may not be sharp and thus thevalue of D(central-cornea) may depend on the particular definitionadopted.

In light of these values, some matching embodiments of the contactelement 340 can have a central-diameter Dc in the 6-9 mm range, in somecases in the 8-9 mm range. Embodiments can also have aperipheral-diameter Dp in the 10-14 mm.

For completeness of the discussion, here we reproduce thatR(central-cornea) typically falls in the 7-8 mm range, with a averagevalue of about 7.6 mm; R(peripheral-cornea) in the 8-11 mm range; andR(sclera) in the 9-14 mm range, often in the 9.5-12 mm range.

Returning to the discussion of the diameters, FIG. 3 illustrates that insome embodiments, while the central-diameter Dc of the contact element340 may track the complex frontal eye surface in general, but it may notbe precisely aligned or matched with either D(central-cornea) orD(peripheral-cornea). Rather, the central-diameter Dc can fall betweenthese values. Embodiments with this feature may have an additionaladvantage beyond (1) structure matching, and (2) radius matching, asdiscussed next.

(3) Lateral Stretching:

As shown in FIG. 3, in some embodiments an edge 346 can be formed at thecentral-diameter Dc, where the central portion 342 and the peripheralportion 344 are joined, because the central radius Rc is different fromthe peripheral radius Rp. In embodiments whereD(central-cornea)<Dc<D(peripheral-cornea), upon docking, the edge 346lands on the peripheral-cornea 23. Since the radius of curvature of thecentral portion Rc is not equal to the radius of curvature of theperipheral-cornea R(peripheral-cornea), the contact element 340 at theedge 346 may not smoothly match the peripheral-cornea 23, but ratherpress or wedge into it as the docking starts. As the docking proceeds,this wedged edge 346 can laterally stretch the peripheral-cornea 23 andthus the central-cornea 21, in a sense “ironing out” wrinkles that mayhave started to form by the docking pressure. This is an additionaladvantage of the bi-radial design of the contact element 340 that isespecially effective when the edge 346 with the central-diameter Dc islarger than the diameter of the central-cornea 21: D(central-cornea)<Dc,and smaller than the diameter of the peripheral-corneaD(peripheral-cornea): Dc<D(peripheral-cornea). As discussed above, formost eyes, D(central-cornea) falls in the 6-9 mm range, andD(peripheral-cornea) in the 10-12 mm range, thus the above inequalitybroadly translates to Dc falling in the 6-12 mm range. In someembodiments Dc may fall in the 8-10 mm range.

This stretching or ironing functionality can be especially effective ifa contact element 340 is chosen for a patient that has a central radiusof curvature Rc that is slightly smaller than the radius of curvature ofthe central-cornea R(central-cornea) of the patient.

To sum up the above considerations: the bi-radial contact elements 340can provide a performance superior to the existing contact lenses, whosenon-matching, single-radius-of-curvature design flattens and wrinklesthe cornea, because embodiments of the here-described bi-radial contactelements can offer one or more of (1) structure matching, (2) radiusmatching, and (3) lateral stretching of the cornea, all of these effectsbeing capable of reducing the wrinkling of the cornea.

Some embodiments of the contact element 340 can go even further andmatch the three-portion structure of the anterior surface of the eye. Insome embodiments, the contact element 340 can have a central portionwith a central-radius of curvature Rc in the 7-9 mm range to align withthe central-cornea 21, an intermediate portion with an intermediateradius of curvature Ri in the 8-12 mm range to align with theperipheral-cornea 23 and a peripheral portion with a peripheral radiusof curvature Rp in the 10-14 mm range to align with the sclera. In someembodiments these three radii are related as: Rc<Ri<Rp. Such a contactelement that matches the structure of the frontal eye surface andapproximates its three radii may cause an even more limited cornealwrinkling. Such patient interfaces and contact elements can be termed“tri-radial”.

In addition, as discussed at (3) above, if one or both of the diametersseparating the three regions of such a tri-radial contact element arenot aligned with D(central-cornea) and D(peripheral-cornea), that canlead to a beneficially enhanced lateral stretching effect.

In some embodiments, the contact portion 320 can include an escapestructure to assist an expulsion of air from the contact space betweenthe contact element 340 and the cornea. This escape structure can takevarious forms, such as radial channels or a rounding of the edge 346along short arc segments.

The bi-radial structure of the contact element 340 has a further aspect:during docking the bi-radial structure can assist the centering of thepatient interface 300. In a case when the bi-radial contact element 340makes its initial contact with the cornea in a de-centered position, theedge 346 and the bi-radial contacting surfaces can exert lateral forcesthat can laterally move the eye until it reaches a more centeredposition. This self-centering can also be made more effective if alubricating liquid is applied to the contact surface.

In some embodiments, the distal lens 330 can be rigid or have reducedflexibility. The distal lens 330 can accommodate a proximal surface ofthe contact element 340, preventing a more than 5% radial deformation ofthe contact element 340 upon docking to the eye (ΔRc/Rc<5%). In someembodiments, this is achieved by employing a distal lens 330 with adistal surface radius of curvature that is approximately matched to aproximal surface radius of curvature of the contact element 340.

In some embodiments, the contact portion 320 may include an affixationstructure 350 to affix the contact element 340 to the contact portion320 along a perimeter. The affixation structure 350 can be configured toprevent a more than 5% lateral deformation of the contact element 340upon docking to the eye. To achieve this functionality, the affixationstructure 350 can include an affixation groove, a support rim, aninsertion structure, an interlocking structure, a slide-in structure, apop-in structure, or a lock-in structure.

In some embodiments where the distal lens 330 can limit the radialdeformation of the contact element 340 and the affixation structure 350can limit its lateral expansion, the contact element 340 can be made ofa soft material with low compressibility. An example can be a contactelement 340 with high water content. Such a contact element 340 canlubricate the contact surface well and can adjust its shape locally to asmall degree to accommodate the corneal surface upon docking, bothfactors reducing corneal wrinkling. At the same time, since the distallens 330 and the affixation structure 350 do not allow for substantialradial or lateral deformations, such a contact element 340 still retainsits overall shape and radii, thus providing a known and well-controlledoptical path for the laser beam 112, minimizing its astigmatism anddistortions.

In the embodiments above, the contact element 340 can be manufactured tobe part of the contact portion 320 and thus part of the patientinterface 300. In other embodiments, the contact element 340 can beprovided as a separate element, for example hydrated in a pouch filledwith an aqueous solution to prevent drying. Such contact elements 340can be configured to be inserted into the contact portion 320 during apreparatory step of the ophthalmic surgery by a surgeon or otherqualified personnel. In such embodiments, the contact portion 320 can beconfigured to accept the insertion of the contact element 340.

The contact portion 320 may accommodate the insertion of the contactelement 340 by having an embodiment of the affixation structure 350 thatcan be an affixation groove, a support rim, an insertion structure, aninterlocking structure, a slide-in structure, a pop-in structure, or alock-in structure. In any of these embodiments, the affixation structure350 can be configured to firmly affix the inserted contact element tothe contact portion, and to prevent a more than 5% lateral expansion orbulging of the contact element upon the docking to the eye.

Further, in some embodiments, the contact portion 320 can include anembodiment of the rigid distal lens 330, having a distal surface with adistal radius of curvature within 5% of a proximal radius of curvatureof a proximal surface of the contact element 340. In these embodiments,the distal lens 330 can form an extended contact with the contactelement 340 upon its insertion, and can prevent a more than 5% radialdeformation of the contact element upon the docking to the eye. Asdiscussed above, the contact element 340 can be flexible but have lowcompressibility, an example of which can be materials with high watercontent.

Because of the outlined embedding geometry of the distal lens 330 andthe affixation structure 350 and because of its low compressibility, thecontact element 340 is largely prevented from bending, deforming,stretching, compressing and bulging once inserted into the contactportion 320, thus retaining its shape to a high degree when docked tothe eye.

In these embodiments, while the contact element 340 can broadly matchthe structure and the radii of the central cornea and that of thesclera, small mismatches can remain as the precise values of these radiivary from patient to patient. Therefore, when docking the patientinterface 300 to the eye, the central-cornea 21 and the contact element340 may still need to deform to a small degree to accommodate theseremaining small mismatches. As just outlined, in some embodiments, thedistal lens 330, the affixation structure 350, and the central radius ofcurvature Rc can be selected such that they largely prevent the contactelement 340 from deforming, stretching, and bending. Moreover, amaterial of the contact element 340 can be selected to make thecompressibility of the contact element 340 low, thus preventing acompression of the contact element 340 as well. In such designs of thecontact element 340, the central-cornea 21 may deform to a considerablylarger degree than the contact element 340 upon docking. In numericalterms, a change of the radius of curvature of the central-corneaR(central-cornea) can be greater than a change of the central radius ofcurvature Rc of the contact element 340: ΔR(central-cornea)>ΔRc. Inother embodiments, the central corneal deformations can be substantiallylarger than the deformations of the contact element 340 upon docking.The docking of these embodiments can be characterized byΔR(central-cornea)>3ΔRc, ΔR(central-cornea)>5ΔRc and in some embodimentsΔR(central-cornea)>10ΔRc.

The choice of material of the contact element 340 can play a role inensuring the above described attributes. In some embodiments, thecontact element 340 can include a contact material that forms alubricating film at the surface of the cornea. The lubrication can bemade effective by a surface of the contact element 340 including ahydrophilic material. Hydrophilic materials not only lubricateefficiently, they can also reduce fogging of the contact element 340which otherwise could present a problem during docking.

An embodiment of the contact material of the contact element 340 can behydrogel. Typically, hydrogel can include a blend of fluorosilicone andhydrophilic monomers. Various embodiments of hydrogel can have widelyvarying water content, having different lubricating and opticalproperties and different compressibilities. By some classifications, ahydrogel is referred to as having low water content if its water content(by refractometer or by weight) is in the 10-50% range, in some cases inthe 30-50% range, medium if the water content is in the 50-70% range,and high, if the water content is above 70%. The water content can bereached and maintained by hydrating the contact element 340 in anaqueous solution, an example of which can be saline.

Once hydrated, the contact element 340 can have a hydrated index ofrefraction in the range of 1.32-1.44, providing a close match with theindex of refraction of the cornea, about 1.37.

The higher the water content, the more the contact element 340 islubricating the contact surface with the central-cornea 21, furtherreducing the causes of wrinkling.

FIG. 3 also shows that the contact portion 320 can include a suctionring or suction skirt 322, to be coupled to a suction system through asuction port 324, to receive a suction from the suction system, and toapply the suction of the suction system to a contact space between thepatient interface 300 and the eye 20 to dock the patient interface 300to the eye firmly.

FIG. 3 also illustrates that in some embodiments of the patientinterface 300, the attachment portion 310 and the contact portion 320can be integrated portions of the patient interface 300. They can befirmly integrated during the manufacturing process, sometimes evenformed from the same single plastic material.

FIG. 4 illustrates that in some other embodiments, the attachmentportion 310 can be separate from the contact portion 320. In suchembodiments, the freely movable contact portion 320 can be first dockedto the eye 20 with ease. Once the eye 20 is captured by the contactportion 320, the contact portion 320 can be used to manipulate and alignthe eye 20 with the attachment portion 310 that is harder to move sinceit is attached to the hard-to-adjust ophthalmic laser system 100. Oncealignment is achieved, the contact portion 320 can be coupled to theattachment portion 310.

FIG. 5 illustrates a method 400 of docking a patient interface to aneye. Method 400 can include the following steps. Step 410 can includedetermining R(central-cornea), a radius of curvature of a centralportion of a cornea, and R(peripheral-cornea-sclera), a radius ofcurvature characteristic of a peripheral portion of the cornea and asclera of a procedure eye. For example, R(peripheral-cornea-sclera) canbe a value between R(peripheral-cornea) and R(sclera) of the eye. Step420 can include selecting a contact element with a central portionhaving a central radius of curvature Rc and a peripheral portion havinga peripheral radius of curvature Rp that is greater than Rc. In relationto step 420, the contact element can be selected to have Rc less thanR(central-cornea)+1.0 mm, and Rp less thanR(peripheral-cornea-sclera)+1.0 mm. Finally, step 440 can includedocking the patient interface of an ophthalmic surgical laser systemwith the selected contact element to the eye. In some embodiments ofselecting 420, the contact element can be selected to have Rc less thanR(central-cornea)+0.75 mm, and Rp less thanR(peripheral-cornea-sclera)+0.75 mm. In yet other embodiments ofselecting 420, the contact element can be selected to have Rc less thanR(central-cornea)+0.5 mm, and Rp less thanR(peripheral-cornea-sclera)+0.5 mm.

In the steps of the method 400, the elements can be related to theanalogous elements of the embodiments of FIGS. 1-4. In particular, thepatient interface can be the patient interface 300, the procedure eyecan be the eye 20, the contact element can be the contact element 340and the ophthalmic surgical system can be the ophthalmic surgical system100.

As described before, contact elements with the above characteristics canmatch the bi-radial structure of the frontal surface of the eye. Withthe radii Rc and Rp in the described ranges, they can provide a closematch to both the central-cornea and the sclera. As also describedearlier, the central and the peripheral portions can meet at an edgethat can have a stretching or ironing effect on the cornea, furtherreducing the wrinkling. This stretching or ironing effect can beparticularly effective if the selecting 420 includes selecting a contactelement with a central radius of curvature Rc less thanR(central-cornea).

The method 400 can further include inserting the selected contactelement into the patient interface before docking, in embodiments wherethe contact element is provided separately from the patient interface.In some of these embodiments, a manufacturer can provide a patientinterface and a set of contact elements for the operating surgeon. Afterthe surgeon determines R(central-cornea) andR(peripheral-cornea-sclera), she or he can select the contact elementwhose central radius of curvature Rc and peripheral radius of curvatureRp are the most suitable in light of the determined radiiR(central-cornea) and R(peripheral-cornea-sclera), and thus promise tobest achieve the surgical goals.

In other embodiments, the contact element can be already installed orinserted into the patient interface during manufacture. In theseembodiments, the selecting 420 can include selecting the patientinterface from a set of patient interfaces that has the selected contactelement.

In some embodiments of the method 400 the determining 410 can includegenerating a depth-image of an anterior portion of the eye anddetermining R(central-cornea) and R(peripheral-cornea-sclera) from thedepth-image. The depth-image can be generated by an Optical CoherenceTomography (OCT) system, a Scheimpflug system, or a slit lamp.

While this document contains many specifics, these should not beconstrued as limitations on the scope of the invention or of what may beclaimed, but rather as descriptions of features specific to particularembodiments of the invention. Certain features that are described inthis document in the context of separate embodiments can also beimplemented in combination in a single embodiment. Conversely, variousfeatures that are described in the context of a single embodiment canalso be implemented in multiple embodiments separately or in anysuitable subcombination. Moreover, although features may be describedabove as acting in certain combinations and even initially claimed assuch, one or more features from a claimed combination can in some casesbe excised from the combination, and the claimed combination may bedirected to a subcombination or a variation of a subcombination. Also,variations and enhancements of the described implementations, and otherimplementations can be made based on what is described.

1-28. (canceled)
 29. A patient interface for an ophthalmic system,comprising: an attachment portion, configured to attach the patientinterface to a distal end of the ophthalmic system; a contact portion,configured for docking the patient interface to an eye; and a contactelement, coupled to the contact portion, comprising a pre-formed shapethat includes, prior to contact with a surface of a cornea of the eye aspart of the docking of the patient interface to the eye: a transparentcentral portion with a central radius of curvature Rc; a transparentperipheral portion with a peripheral radius of curvature Rp, wherein Rcis smaller than Rp; and an edge structure where the transparent centralportion and the transparent peripheral portion are joined, the edgestructure having a central diameter Dc in the range of 6-12 mm.
 30. Thepatient interface of claim 29, wherein: Rc is in a range of 6.6 mm-9.1mm and Rp is in a range of 8.8 mm-10.8 mm.
 31. The patient interface ofclaim 29, wherein: Rc is in a range of 7.1 mm-8.1 mm and Rp is in arange of 9.3 mm-10.3 mm.
 32. The patient interface of claim 29, wherein:the central diameter Dc of the edge is in the range of 8-10 mm; and theedge structure is configured to stretch a peripheral-cornea area of theeye during docking.
 33. The patient interface of claim 29, wherein: theedge structure is configured to laterally stretch a central-cornea ofthe eye during the docking.
 34. The patient interface of claim 29, thecontact portion comprising: an escape structure, configured to assist anexpulsion of air from a contact space between the transparent centralportion and the central-cornea.
 35. The patient interface of claim 29,comprising: a rigid distal lens, configured to: accommodate a proximalsurface of the contact element; and prevent a more than 5% radialdeformation of the contact element upon docking to the eye; and anaffixation structure, configured to: affix the contact element to thecontact portion along a perimeter; and prevent a more than 5% lateralexpansion of the contact element upon docking to the eye.
 36. Thepatient interface of claim 29, wherein: the contact element isconfigured for insertion into the contact portion; and the contactportion is configured to accept the insertion of the contact element.37. The patient interface of claim 36, the contact portion comprising: arigid distal lens, having a distal surface with a distal radius ofcurvature within 5% of a proximal radius of curvature of a proximalsurface of the contact element, wherein the distal lens is configuredto: form an extended contact with the contact element upon itsinsertion; and prevent a more than 5% radial deformation of the contactelement upon the docking to the eye.
 38. The patient interface of claim36, the contact portion comprising: an affixation structure, having atleast one of an affixation groove, a support rim, an insertionstructure, an interlocking structure, a slide-in structure, a pop-instructure, and a lock-in structure, wherein the affixation structure isconfigured to: firmly affix the contact element to the contact portionafter the insertion; and prevent a more than 5% lateral expansion of thecontact element upon the docking to the eye.
 39. The patient interfaceof claim 36, wherein: a distal lens, an affixation structure, a materialof the contact element and the central radius of curvature Rc areselected such that upon docking the patient interface to the eye, achange of a radius of curvature of the cornea of the eye is greater thana change of the central radius of curvature Rc: □R(central-cornea)>□Rc.40. The patient interface of claim 29, wherein: the contact elementcomprises a contact material that forms a lubricating film at thesurface of the central-cornea.
 41. The patient interface of the claim29, wherein: a surface of the contact element comprises a hydrophilicmaterial.
 42. The patient interface of claim 29, wherein: the contactelement comprises hydrogel with a water content above 70%.
 43. Thepatient interface of claim 29, wherein: the contact element compriseshydrogel with a water content in a range of 50-70%.
 44. The patientinterface of claim 29, wherein: the contact element comprises hydrogelwith a water content in a range of 30-50%.
 45. The patient interface ofclaim 29, wherein: the contact element has a hydrated index ofrefraction in the range of 1.32-1.44.
 46. The patient interface of claim29, the contact portion comprising a suction ring configured to: becoupled to a suction system; receive a suction from the suction system;and apply the suction of the suction system to a contact space betweenthe patient interface and the eye to dock the patient interface to theeye.
 47. The patient interface of claim 29, wherein: the attachmentportion and the contact portion are integrated portions of the patientinterface.
 48. The patient interface of claim 29, wherein: theattachment portion is separate from the contact portion; and theattachment portion is configured to be coupled to the contact portionafter the contact portion has been docked to the eye.
 49. The patientinterface of claim 29, wherein: the edge structure is further configuredto press on the surface of the cornea as the docking starts andlaterally stretch a central-cornea of the eye as the docking proceeds toreduce corneal wrinkles caused by the docking; and the contact elementcomprises the transparent central portion with the central radius ofcurvature Rc, the transparent peripheral portion with the peripheralradius of curvature Rp, and the edge structure independent of contactwith the eye.